With a conventional computer system, computer resources (hereinafter referred to as the resource(s)) mounted in a physical server machine are firstly occupied by an OS (Operating System). Then, a software management program operating on the OS secures a specified amount of resources among the resources recognized by the OS in accordance with a predetermined definition. The above-described software management program is software that provides application software with a higher-level and more specific function than that of the OS; and, for example, middleware can be an example of the software program. Furthermore, the software management program allocates the resources to application software operating on the software management program in accordance with a predetermined definition.
However, with the above-described computer system, the OS detects a new resource at the time of activation and occupies the resource, but it has to manually change the definition of the resource amount secured by the software management program. Also, the definition of the resource allocation to the business application software needs to be changed manually. Accordingly, when the resource amount required by the entire system changes, it is necessary to stop the system once and then increase or decrease the physical resource.
Incidentally, with recent computer systems, a virtual machine technique to virtually divide physical resources of a server system by using software and construct a plurality of “virtual machines” on the server is implemented. This virtual machine technique can deploy a plurality of virtual machines on one physical server and operate an OS independently at each virtual machine. Under this circumstance, a resource amount allocated to each virtual machine can be flexibly divided without being bound by the configuration of the physical resources and the resource amount can be changed dynamically without stopping the system. Therefore, even when the resource amount required by the entire system changes, the resource amount which can be used by the OS of each virtual machine can be increased or decreased flexibly without stopping the system once.
However, although the OS of each virtual machine can flexibly increase or decrease the available resource amount as described above, the software management program operating on the OS does not have a function that detects a change of the resource amount or automatically identifies business application software. So, the software management program cannot dynamically manage the resources secured by itself or the resources to be allocated to the business application software.
Therefore, when the resource amount required by the entire system changes, a technique to prepare a virtual machine itself separately, that is, to promptly enhance computer performance by a so-called scale-in/scale-out method is disclosed (for example, Patent Literature 1). According to Patent Literature 1, when the resource amount of the entire system changes, the influence of a change in the settings of the software management program can be reduced by preparing a virtual machine separately and increasing or decreasing the resource amount.